This invention pertains to the searching of documents and, more particularly, to the searching of documents that have been protected by encryption.
In the past, buyers inspected goods before they purchased them. For instance, a buyer would enter a book store and browse numerous magazines and, under the observation of book store personnel, view books before purchasing specific books and/or magazines. Thus, the buyer had an opportunity to review the books and/or magazines before purchasing them.
In today""s society, with the proliferation of personal computers and the ability to easily connect to the internet, sometimes potential buyers have the ability to review and copy material before they purchase the material. In other instances, the buyers must purchase the material before they have an opportunity to review the material.
Sometimes, owners of textual material prepare a summary of the material they have for sale so that search engines and potential purchasers may find and review the material before purchasing the material. The foregoing works well for non-encrypted textual documents. However, secure or encrypted documents can not be searched. A non-encrypted abstract of a protected encrypted document may solve the above problem since the abstract may be searched. However, the creation of an abstract is expensive and time-consuming. Abstracts are often abridged and do not always contain the information present in the article being searched.
If the owners of textual material encrypted the material before the material is made available, search engines would not be able to search the encrypted material, and potential buyers would have to purchase the material before having a chance to review the material. If the owners of textual material made the material available in plain text, search engines would be able to find the material, and potential buyers may not want to purchase the material, since they have already seen the material.
Digital Rights Management (DRM) packages have been developed to encrypt the text of documents and control a user""s access to the document. The restrictions imposed by Digital Rights Management packages often made it difficult for a potential buyer to search a set of documents efficiently without paying for each access to the document (pay per view) or only consuming a limited number of accesses. Hence, a potential buyer may be penalized for searching a document which may or may not be relevant to the buyer""s interest.
This invention overcomes the disadvantages of the prior art by providing an electronic-based method that allows a search engine to find a document allowing a potential buyer to review portions of the document. The invention provides a plain text index to the document that may be searched by search engines and reviewed by potential buyers of the document. The full text of the document remains encrypted and managed by a Digital Rights Management (DRM) package. The index is synchronized and hides contextual information so that potential buyers may determine whether or not they want to obtain rights to review the document. The document may be found in any electronic storage facility, i.e.: the Internet, computer work station, hard disk, computer disk, floppy disk, CD ROM, main frames, etc.
The searchable synchronized index is in plain text in a digital container that protects by encryption a DRM-controlled document. Inclusion of the index in the same digital container as the controlled document ensures proper synchronization of the index and the document.
In some instances, key words in an index may reveal valuable information about the content of the document. For instance, if a document contains a list of the top ten contributors to a political campaign, the key word list may reveal the identity of the contributors. This invention gives the publisher the ability to remove the contributors from the plain text index before the index is included in the digital container. Sensitive words in a document are most likely to be proper names. The proper name key words may be highlighted automatically by comparing all index entries to a standard dictionary and selecting words that are not present. Over time, the publisher of the document may elect to build a list of known sensitive index words which will be excluded automatically from the searchable synchronized index.
The publisher of the document is also given the ability to change the order or relationship of some key words from the searchable synchronized index that may reveal sensitive information or information the publisher does not want to disclose. For instance, the words xe2x80x9cABC Electronics, Inc.xe2x80x9d, xe2x80x9cstrongxe2x80x9d, and xe2x80x9cbuyxe2x80x9d may not be revealing in isolation, but the phrase xe2x80x9cABC Electronics, Inc. strong buyxe2x80x9d may have special meaning if it appears in an analyst""s report about ABC Electronics, Inc. Thus, the relationship or combination of some key words may be significant. One way to conceal the relationship or combination of certain key words is randomizing the searchable synchronized index of key words. Another method for concealing the relationship or combination of certain key words is to use a context independent hashing rule, i.e., storing the key words in alphabetical order.
The publisher or author of the document also is given the ability to mark sensitive regions of the document so that information contained in these regions would be ignored by the index generation software and not be included in the searchable synchronized index.
The number of times that a word appears in a document may also provide useful information to a search engine. This information may be included in the searchable synchronized index, but only if that particular word does not compromise the value of the content. Frequency information may be suppressed entirely in the searchable synchronized index, or techniques, such as a key word list, may be used to select which words are stored with this information in the searchable synchronized index. Frequency information may also be randomized so that a search engine may obtain a sense of the significance of a particular key word without revealing exactly how often it is used.